Before any major procedure, like an upgrade, it is recommended to backup all the data to an external device. In Scylla, backup is done using the nodetoolsnapshot command. For each node in the cluster, run the following command:

nodetooldrainnodetoolsnapshot

Take note of the directory name that nodetool gives you, and copy all the directories having this name under /var/lib/scylla to a backup device.

When the upgrade is complete (all nodes), the snapshot should be removed by nodetoolclearsnapshot-t<snapshot>, or you risk running out of space.

Before upgrading, check what version you are running now using dpkg-sscylla-server. You should use the same version in case you want to rollback the upgrade. If you are not running a 2.1.x version, stop right here! This guide only covers 2.1.x to 2018.1.y upgrades.

Execute the following commands one node at the time, moving to the next node only after the rollback procedure completed successfully.

The following procedure describes a rollback from Scylla Enterprise release 2018.1.x to Scylla 2.1.y. Apply this procedure if an upgrade from 2.1 to 2018.1 failed before completing on all nodes. Use this procedure only for nodes you upgraded to 2018.1

Scylla rollback is a rolling procedure which does not require full cluster shutdown.
For each of the nodes rollback to 2.1, you will:

Drain the node and stop Scylla

Retrieve the old Scylla packages

Restore the configuration file

Restart Scylla

Validate the rollback success

Apply the following procedure serially on each node. Do not move to the next node before validating the node is up and running with the new version.